We plan to produce intragenic recombinants in trpA of E. coli and Salmonella typhimurium. We will use our restriction site maps and nucleotide sequence data to locate the positions of genetic exchanges and to determine the number of sequence switches associated with each exchange. We will determine whether the recombinant tryptophan synthetase alpha proteins are fully functional. We will locate the promoters and regulatory regions of the tna and trpS operons and determine the mechanism(s) of regulation of each of these genes. We plan to use methylation protection and footprinting studies to determine the base pairs in the homologous trp and aroH operators that interact with the trp repressor. We will introduce a DNA fragment containing trpR into other plasmids, downstream from strong promoters, in an effort to produce large amounts of the trp aporepressor. We will continue our studies on attenuation and focus on characterization of the transcription termination complex at the trp operon attenuator. We will continue our attempts to clone genes of neurospora crassa that are concerned with tryptophan metabolism.